Skip to content

Instantly share code, notes, and snippets.

@khanlou

khanlou/StateMachine.swift

Created October 21, 2016 00:14
Show Gist options

  • Select an option

    Learn more about clone URLs
  • Save khanlou/60c4fd0baa457b7a621a74ee599be867 to your computer and use it in GitHub Desktop.

Select an option

Learn more about clone URLs
Save khanlou/60c4fd0baa457b7a621a74ee599be867 to your computer and use it in GitHub Desktop.
Download ZIP

Revisions

  1. khanlou revised this gist Oct 21, 2016. No changes.
  2. khanlou created this gist Oct 21, 2016.
    29 changes: 29 additions & 0 deletions StateMachine.swift
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,29 @@
    protocol State {}

    struct Transition<From: State, To: State> {
    let transition: () -> To
    }

    struct Machine<CurrentState: State> {

    var state: CurrentState

    func transition<To>(with transition: Transition<CurrentState, To>) -> Machine<To> where To: State {
    return Machine<To>(state: transition.transition())
    }
    }

    struct Pending: State {}
    struct Loading: State {}
    struct Loaded: State {}
    struct Failed: State {}

    let kickoff = Transition<Pending, Loading>(transition: { return Loading() })

    let finishLoading = Transition<Loading, Loaded>(transition: { return Loaded() })

    let machine = Machine<Pending>(state: Pending())

    let newMachine = machine.transition(with: kickoff) // compiles
    newMachine.transition(with: finishLoading)
    machine.transition(with: finishLoading) // Cannot convert value of type 'Transition<Loading, Loaded>' to expected argument type 'Transition<Pending, _>'